Classical philosophy and Darwinian biology are far more compatible than is usually assumed. In fact, looking at either from the standpoint of the other can enrich and deepen our appreciation of both. From a Darwinian point of view, the theories of Plato and Aristotle deserve to be taken very seriously. From the classical point of view, Darwinian biology is much less reductionist than its enemies suppose.

Saturday, June 29, 2013

Group Selection and the Evolution of Morality

Perhaps the best single article
I have read on the group selection debate is “Evolution
‘for the Good of the Group’”, in American
Scientist, September-October 2008.It is another collaboration between the two Wilsons, E. O. and D.S.I would add that it is also a very good
introduction to the general question of the levels of selection‑genes,
individuals, and groups, within a population.

Group selection is one
explanation for the evolution of altruism.Any time one organism (or any unit within an organism) behaves in such a
way as to confer a reproductive advantage to another organism at its own
expense, this is evolutionary altruism.Honey
bee workers who serve the queen but do not themselves reproduce are behaving
altruistically.A vampire bat who regurgitates
some hard won blood to feed a hungry roost mate is another example.Many examples of altruism are easily
explained in terms of deferred gratification (reciprocity) or benefit to
closely related individuals (kin selection).

Group selection theory is based
on the claim that some altruistic behaviors are selected for because they
benefit the group without any return to the altruist whether direct (deferred
gratification) or indirect (kin selection).A group with more altruists will be more reproductively successful than
a group with fewer and so altruists may increase in the total population, at
least initially.Increase in the total
population is what we mean by evolution.

There seems to be an
insuperable problem.While between group
selection might well favor altruistically endowed groups, within group
selection will favor the selfish over the public spirited organisms.Altruists would seem to be doomed to
inevitable extinction as their selfish fellows outbreed them.In this view, which held the field for a long
time, group selection is unsustainable.

However, group selection does in
fact occur.Wilson and Wilson present a
number of forceful examples.My favorite
is the bacterium Pseudomonas fluorescens.

When this species is cultured in an unstirred broth, the
cells soon consume most of the oxygen in the bulk of the medium, so only a thin
layer near the surface remains habitable. A spontaneous mutation called wrinkly
spreader causes cells to secrete a cellulosic polymer that forms a mat and
helps them colonize the water surface. Production of the polymer is
metabolically expensive, which means that nonproducing “cheaters” have the
highest relative fitness within the mat; they get the benefit of the mat
without contributing to its upkeep. However, if the proportion of cheaters
grows too high, they are undone by their own success. The mat disintegrates,
and the entire group sinks into the anoxic broth. Experiments by Paul B. Rainey
and Katrina Rainey have shown that the wrinkly spreader trait is maintained in
the population by group selection, even though it is disadvantageous within any
one group.

This example illustrates the
fact that the “free rider problem” is real.The benefits of altruism in between group selection can indeed be undone
when selfish cheaters crowed out the altruists.At the same time, the very fact that mats form at all demonstrates that
group selection was a powerful force in the evolution of this microbe.Wrinkly spreader can only be maintained by
its benefit to the community.

Obviously, what is needed to
maintain group selection is some mechanism for suppressing cheating.I have no idea how this is done by bacteria
but Christopher Boehm has a good idea how it is done among human hunter
gatherers.He argues in Moral Origins that social selection
(reproductive benefits that result from a reputation for altruistic behavior)
and sanctions against bullies (free riders) functioned to protect altruists
from cheaters.

Human beings are extraordinarily
capable of altruism toward unrelated individuals.Explaining this is a big challenge for
evolutionary theory.Boehm considers a
number of explanations that are current in the scholarship.He doesn’t reject them, but argues that some
of them work only when cheating is suppressed by the mechanisms mentioned
above.

In Plato’s Gorgias, Socrates argues that justice is analogous to medicine: it
is a response to dysfunction in the social body.I am inclined to think that the theory of
group selection is beginning to uncover something like the Platonic idea of
justice.It may be that retribution is
something that shapes all life on earth.